22 ACTA BOT. CROAT. 84 (1), 2025 Acta Bot. Croat. 84 (1), 22–26, 2025 CODEN: ABCRA 25 DOI: 10.37427/botcro-2025-002 ISSN 0365-0588 eISSN 1847-8476 Rapid spread of the Mediterranean glycophyte Catapodium rigidum in Hungary Norbert Bauer1*, János Csiky2, Attila Mesterházy3, Mátyás Wolf4, Dávid Schmidt5 1 Hungarian Natural History Museum, Department of Botany, Könyves K. krt. 40, H-1089 Budapest, Hungary 2 University of Pécs, Department of Ecology, Ifjúság u. 6, H-7624 Pécs, Hungary 3 Hunyadi utca 55, H-9500 Celldömölk, Hungary 4 Árvácska utca 38, H-7451 Kaposvár, Hungary 5 Sopron University, Institute of Environmental Protection and Nature Conservation, Bajcsy-Zsilinszky u. 4, H-9400 Sopron, Hungary Abstract – This paper discusses the spread of the Mediterranean plant Catapodium rigidum (L.) C.E. Hubb. in Hungary, which is found in the transition zone between the sub-Mediterranean and continental climatic zones of Central Europe. This alien species has been found at 12 new localities in Hungary in recent years. Some of these stands are located along main roads, while others are found in urban weed vegetation. The species was most likely introduced by increasing road traffic and tourism. Our preliminary findings suggest that the spread of the species is not concentrated along main roads due to its salt sensitivity. Instead, it is more likely to be found in xerothermic weed vegetation in urban areas where salting and winter de-icing are not applied. Keywords: agochory, anthropochory, global warming, Poaceae, urban flora, weed species Introduction Catapodium rigidum (L.) C.E. Hubb. (Desmazeria rigida (L.) Tutin), fern grass or rigid-fescue (Poaceae family), is one of the most common synanthropic weed species in the Med- iterranean region. It occurs in dry stony grasslands, particu- larly in ruderal places along roadsides, and municipal areas (Coste 1906, Fiori 1923, Jávorka 1925, Horvat et al. 1974). A recent study by Jasprica et al. (2017) found that this species is one of the most widespread weed species in railway sta- tions in the North-Western Balkans. Catapodium rigidum s. str. has a Mediterranean-Atlantic distribution (Rikli 1943–1948, Meusel et al. 1965, Tutin et al. 1980). However, fern grass has been known to occur adventitiously in areas far from its original range, such as Asia, North and South America, Southern Africa, Australia (Clark 1974, Bhat et al. 2021, GBIF 2023). The species is considered indigenous to a small part of Switzerland (between Sézegnin and Soral), but introduced occurrences have also been long known in sev- eral large towns and cities, at railway stations, along railway lines, and in several cities in Germany (Hegi 1935, Buttler et al. 2018). Very few occurrences have been reported in Central Europe, east of Germany. Its casual occurrence was reported for the first time from Graz, Austria (Melzer 1954). The first report of this species in the Czech flora was almost 50 years ago by Dostál (1989), but there have been no con- firmations. In 2009, Stöhr et al. reported a second observa- tion of fern grass in Austria, in the surroundings of Salzburg (the community of Lamprechtshausen). Old data (published or herbarium) reported occasional introductions of many Mediterranean species in Hungary. An accelerated spread of such plants has been observed re- cently (see Schmidt et al. 2016, Kun et al. 2023). However, in the BP herbarium specimens of C. rigidum originated from 19th century and the plants were grown from seeds in the botanical garden. Neither Borbás (1891) nor Filarszky (1894) mentioned it in their related papers. The species was first observed in Hungary by Solymosi (2008) along the main road near Becsehely (Zala County, Western Hungary). A decade later, Schmidt (2019) reported a finding of the spe- cies on the Szombathely bypass (Vas County, Western Hun- gary). In recent years, the species has been found in many * Corresponding author e-mail: bauer.norbert@nhmus.hu mailto:bauer.norbert@nhmus.hu RAPID SPREAD OF CATAPODIUM RIGIDUM ACTA BOT. CROAT. 84 (1), 2025 23 locations, particularly in the western part of the country (Transdanubia). While the manuscript of this study was be- ing written, Rigó et al. (2023) reported the species from the capital (Budapest) in a single locality. The aim of our study is to provide a comprehensive summary of the current dis- tribution of C. rigidum in Hungary, based on both published and unpublished data. Material and methods All authors conducted independent fieldwork, examin- ing roadside vegetation and urban areas in various regions of the country. We recorded the geographic coordinates of the occurrences using GPS devices. A list of the sites is provided, along with the observation dates, geographical coordinates, grid numbers in the Central European Flora Mapping System (Niklfeld 1971), estimated number of individuals, and occurrence conditions. The specimens col- lected from the new sites in Hungary have been deposited in the BP and JPU Herbaria (Thiers 2024). Results The oldest specimens of Catapodium rigidum collected in Hungary were obtained from plants grown from seeds sown in a botanical garden (leg. Fekete, 30.10.1903, culta in h. bot. Budapest BP 313807, 408777). Recent spontaneous occurrences are summarised in Tab. 1. The distribution pattern of the species in Hungary (Fig. 1) indicates a spread in Western and Southern Transdanu- bia. The species was predominantly found in high-traffic locations, such as main roads and popular tourist areas. Tab. 1. Introduced occurrences of Catapodium rigidum found in Hungary until the end of 2023. CEU = grid number of the Central European Flora Mapping System (Niklfeld 1971). CEU Settlement Locality Coordinate Habitat Number of individuals Date Observer / Collector Herbarium specimen 9566.2 / 9566.4 Becsehely main road 7 – road bank no data 2007 P. Solymosi – 8765.4 Szombathely main road 86 (E65) N 47.221971 E 16.658571 road bank appr. 200 2017, 2019- on- wards D. Schmidt – 8965.2 Egyházasrádóc main road 86 (E65) N 47.104442 E 16,637393 monodominant along road bank 1000 22.06.2022. N. Bauer HNHM-TRA 00129733, HNHM-TRA 00129734 8965.4 Körmend main road 86 (E65) N 47,025314 E 16, 365181 asphalt road edge < 20 26.06.2022. A. Mesterházy – 9975.1 Pécs Tettye, Zöldfa street N 46.081557 E 18.232826 along the pavement and the asphalt road 10–20 25.05.2023. M. Wolf – 8765.4 Szombathely main road 86 (E65) N 47.221971 E 16.658571 smaller stand on road bank 100 28.05.2023. D. Schmidt HNHM-TRA 00702573 8480.1 Budapest III. District, Gyűrű street N 47.598549 E 19.060334 small trampled lawn patch and crevices of pavement ~400 31.05.2023. A. Rigó – 9975.1 Pécs Tímár street (in the city centre) N 46.074521 E 18.233905 in a one-way street with limited traffic, at the foot of the buildings 10-20 16.06.2023. J. Csiky JPU 9364.4 Rédics main road 86 (E65) N 46.618997 E 16.465032 massive population along road bank 1000 17.06.2023. D. Schmidt HNHM-TRA 00702574 9172.4 Balatonszemes pedestrian section at yacht harbor N 46.812442 E 17.770822 under the strip of shrubs at the edge of the sidewalk, few < 20 18.06.2023. N. Bauer & A. Hüvös- Récsi HNHM-TRA 00702591 9270.3 Balatonmáriafürdő interior area, Keszeg street N 46.703155 E 17.375309 sidewalk edge, car driveway 10–20 30.06.2023. D. Schmidt – 9270.4 Balatonfenyves interior area, at the crossing of Kölcsey street and the railway N 46.712215 E 17.478821 asphalt road edge < 20 02.07.2023. N. Bauer HNHM-TRA 00702590 BAUER N., CSIKY J., MESTERHÁZY A., WOLF M., SCHMIDT D. 24 ACTA BOT. CROAT. 84 (1), 2025 Discussion Our presumption is that the presence of the fern grass in Hungary can be attributed to human activities, particu- larly international transport and tourism. The type of dis- persal can be classified as anthropochory and agochory, as described by van der Maarel (2005) and Schulze et al. (2005). Where heavy traffic occurs on main roads (roadsides, roundabouts, pavements), the vector could be mainly motor vehicles carrying propagules on pieces of gravel. However, small populations found at sites where waste accumulates (e.g. Balatonszemes harbour; Pécs, at the base of buildings in a one-way street) suggest that lesser amounts of propa- gules may have been transported by human clothing and tools. The current new occurrences may be the result of in- dependent introductions. Although mentioned as a synanthropic species by Hegi (1935), its recent distribution in Europe (Fig. 2. GBIF) is rather dispersed and scattered outside of its original climatic requirements, specifically outside of the regions with oceanic and Mediterranean climates. Fig. 1. Current known occurrences of Catapodium rigidum in Hungary (December 2023). The red triangle shows the places where Catapodium rigidum was found: 1 – Szombathely, 2 – Egyházasrádóc, 3 – Körmend, 4 – Rédics, 5 – Becsehely, 6 – Balatonmáriafürdő, 7 – Balatonfenyves, 8 – Balatonszemes, 9 – Pécs, 10 – Budapest. Fig. 2. Distribution of Catapodium rigidum in Europe based on GBIF data (2 October 2023). The dots show the reported occurrences of C. rigidum, the shades of yellow (from light to dark) reflect the amount of data detected. RAPID SPREAD OF CATAPODIUM RIGIDUM ACTA BOT. CROAT. 84 (1), 2025 25 Its natural distribution limit is almost identical to the January 0 C° isotherm (Michael 2021, p. 52.). Previous oc- currences of this species in Central Europe were sporadic, and for a long time, its presence was not confirmed in Aus- tria and in the Czech Republic (Melzer 1954, Dostál 1989, Stöhr et al. 2009, Pyšek et al. 2012). The establishment of the species in continental areas has been restricted, due to the limiting effect of winter frost (see Manley 1958, Grimm et al. 2008). However, according to the current climate change trends in the Pannonian region (Bartholy et al. 2014), the species is predicted to become established in Central Europe and other areas with a humid continental climate (Beck et al. 2018). Currently, there are limited and conflicting data regard- ing the survival of plants in the stands. In the city of Szom- bathely, it was first discovered in 2017, disappeared for a year, and then reappeared in 2019, remaining present ever since. This observation suggests that if the habitat is suitable self-sustaining populations may develop. Mild winters do not appear to be a limiting factor if there are no periods of heavy frost. However, not all of the stands known for more than two years can be confirmed in the coming year. For instance, one of the most abundant populations found in 2022 (Egyházasrádóc village) was not observed on the road- side during the same period the following year. Given that the winter between the two field surveys of the site was the second mildest in the last 100 years (Szolnoki-Tótiván 2023), it is necessary to consider other limiting factors that may affect the survival of the introduced plants. Occasional mass emergence may occur due to extensive propagule introduc- tion after winter. However, despite significant mass seed dis- persal, germination in the following early spring may not be possible due to the high osmotic stress on roadside verg- es (Davison 1971). According to the Ellenberg-type indica- tor values database (Tichý et al. 2023), the species is presum- ably a glycophyte (salt-sensitive), so the use of salt to de-ice main roads is likely to reduce its long-term viability. The experimental confirmation by Talbi Zribi et al. (2018) also supports the strong salt sensitivity of C. rigidum when planted for forage in arid areas. Additionally, its long-term survival on main road verges may be reduced because C. rigidum is an annual C3 species. Its phenology is character- ised by early spring germination, when the effect of winter salting is still strong and the leaching effect of precipitation is still weak. It is uncertain whether a population, even a relatively large one, can be considered self-sustaining in the future. However, due to the ever-increasing flow of traffic from the Mediterranean, the frequent introduction of its propagules is almost inevitable. It is possible that urban weed vegetation not subject to salting and de-icing will be more likely to have persistent, established populations, even if these are smaller. The aforementioned increases in the chance of establishment are already assumed for many spe- cies with similar climatic requirements and have shown re- cent area expansion (Bátori et al. 2012, Schmidt et al. 2016, Bauer 2018, Mesterházy et al. 2021, Bauer and Verloove 2023, Kun et al. 2023). It is expected that C. rigidum will continue to occur and spread in temperate continental areas of Central Europe, particularly along busy roads and in towns, with an increasing number of observations in the coming years. Acknowledgments We thank everyone who helped us, Annamária Hüvös- Récsi, Zoltán Kenyeres, Attila Rigó, Tamás Wirth in the fieldwork and/or with their remarks. The authors would like to express their gratitude to the two anonymous reviewers for their remarks. 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